Slide-valve mechanism.



No. 795,165. PATBNTED JULY 1a, 1905. L. M. PEM-1T.

SLIDE VALVE MBGHANISM.

ArPLIoATIoN PILBD ma. 4, 1904.

3 SHEETS-SHEET 1.v

L, N @2f M @www N'MMMJ www n CNAM/M on. mumlmlocnmmmu wmlmmmm;

No. r/95,155. PATENTLD JULY 1a, 1905. L. M. PBTTIT.

SLIDE VALVE MBGHANISM.

APPL IIIII 0N' PPPPPP An. 44444 4.

No. 795,165. v PATENTED JULY 18, 1905.

L. M. PETTIT. v

SLIDE VALVE. MEGHANISM.

APPLICATION FILED MAB. 4, 1904. l

3 SHEETS-SHEET 3.

UNITED STATES Patented July 18, 1905.

PATENT OEETCE.

SLIDE-VALVE IVIECHANISIVI.

SPECIFICATION forming part of Letters Patent No. 795,165, dated July 18,1905,

Application filed March 4, 1904. Serial No. 196,616.

T0 all whom, it may concern:

Be it known that I. LAFAYETTE M. PETTIT, a citizen of the United Statesof America, residing at Oripplecreek, in the county of Teller and Stateof Colorado, have invented certain new and useful Improvements in Slide-Valve Mechanism; and I do declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same, referencebeing had to the accompanying drawings, and to the letters of referencemarked thereon, which form a part of this specification.

My invention relates to improvements in slide valve mechanism for steamengines, myv object being to provide a construction of this class inwhich the clearance or the space between the piston and the valve whenthe piston is at its limit of movement in either vdirection shall bereduced to a minimum.

This is an important feature in slide-valve mechanism, since the lessthe volume of steam required to fill the clearance-space the quickerwill the steam-pressure in this space act upon the piston of thecylinder with the full boiler-pressure. Instead of having long passagesextending from the extremities of the cylinder to the steam-chest Iprovide vertical 'passages or ports leading from the extremities of thecylinder to the steam-chest, and instead of having the cylinderreinforced to form a fiat seat where the slide-valve is located thesurface of the valve is formed arc-shaped to conform to the curve of thecylinder, whereby the ports leading from the cylinder to the steam-chestare only of a depth equal -to the thickness of the wall of the cylinder.In this way it is understood that the length of the ports is much lessthan where the top of the cylinder is reinforced to form a iiat base orplatform for the slidevalve. j

Another feature of my improvement is that my improved valve is perfectlybalanced.

Having briefly outlined my improved construction, as well as some of thefunctions it is intended to perform, I will proceed to describe the samein detail, reference being the' valve in a different position.

made to the accompanying drawings, in which is illustrated an embodimentthereof. v

In the drawings, Figure 1 is a vertical longitudinal section takenthrough my improved slide-valve mechanism and extending into thecylinder. Fig. 2 is a similar view showing Fig. 3 is a cross-sectiontaken through the steam-chest at one end and cutting the cylinder. Fig.4 is a horizontal' section of the same. Fig. 5 is a perspective. View ofthe valve, shown in detail. Fig. 6 is a top view of the steam-chest withthe top plate removed. Fig. 7 is a section taken through thepacking-groove of one of the slide-valve heads. Fig. Sis a detailperspective view of the packing construction.

The same reference characters indicate the same parts in all the views.

Let A designate the steam-chest, whose side walls A extend upwardly fromthe cylinder, the steam-chest being closed by a top plate A2. The bottomof the steam-chest is curved to conform to the curve of the cylinder,and the wall of the latter is provided with a vertical port A3, locatedat each end thereof. The slide-valve B is composed of two heads B',connected by a bar B2. The live-steam space is between the heads of thisvalve, while the steam-chest is provided with an exhaust-port A4,located at each end thereof. The heads of the valve are curved toconform to the curve of the cylinder except at their outer extremitiesbeyond the ports A, where the bottom of the steam-chest is composed ofnarrow ledges A5, these ledges being of suiiicient length to form asupport for the heads of the valve during the longitudinal movement ofthe latter. At each end of each head of the valve the latter is providedwith lugs B3, which project inwardly. The function of these lugs is tobalance the valve while it is passing the steam-ports. lf it were notfor these lugs or projections, the upward pressure of the steam, whetherlive or exhaust, on the valve-head while crossing the steam-port wouldthrow the valve out of balance, and thus cause increased resistance toits movement in the steam-chest. The lugs or projections B3, however,project into the steam-chest while the valves are crossing the ports,and the downward pressure of the live steam on these lugs or projectionsneutralizes the effect of the upward steam-pressure on the valve-headswhile crossing the ports. The area of the parts B3 is so regulated as toproduce this result. It will therefore be understood that the parts B3may be made of any suitable size in order to perform the requiredfunction. The bottom of the steam-chest is cut away between the seatsB4, as shown at B, so that as soon as a valve-head has passed beyond thesteam-port into the steam-chest or the space containing the live steamthe parts B3, connected with the valve-head, will project over thereduced part B5 of the bottom of the valve-chest `and allow the livesteam to pass below the said projections, thus neutralizing the eHect ofthese projections after they have performed their function. Eachvalve-head is grooved to receive packing rings or plates B, whichinterlock and overlap each other in such a manner as to make perfectlysteamtight joints. The heads B of the val-ve are of rectangular shapeexcept their bottoms or lower extremities, which are arc-shaped toconform to the curve of the top of the cylinder or bottom of thesteam-chest upon which the valve slides. As shown in the drawings, onehead of the steam-chest is provided with separated lugs B8, havinginwardly-turned outer extremities B. The eccentric-rod C is providedwith a T-shaped head C', adapted to enter or pass between the lugs B8from-v above, after which the eccentric-rod and the valve are connectedin operative relation. The rod may of course be detached from thevalve-head by simply lifting it out of place in a manner that will bereadily understood.

In the drawings the cylinder is designated D, the cylinder-heads D', andthe piston of the cylinder D2.

From the foregoing description it is believed that the use and operationof my improved slide-valve will be readily understood. In Fig. l of thedrawings the slide-valve is shown moved toward the right far enough touncover the ports' E and E. In this case the port E is a live-steamport, through which the live steam passes from the steam-chest A betweenthe valves to the right-hand end ofthe cylinder D and to engagement withthe piston D2, while the port E becomes an exhaust-port, since the steamat the left of the cylinder is passing out of the latter through theport F into one end of the steam-chest at the left of the slide-valvehead and out of a port A4. In the construction shown in Fig. 2 the portE is closed against the live steam, while the port E is still partlyopen to the exhaust, and

the piston under this arrangement must complete its stroke toward theleft by expansion. In this case the steam in the cylinder at the rightof the piston will act on the righthand valve-head B with a tendency toforce the latter upwardly; but the downward pressure of the live steamin the steam-chest on the parts B3 of this valve-head neutralizes theupward pressure of the steam in the cylinder, whereby a perfect balanceof the valve is maintained, while as soon as the right-hand piston Bl ismoved sufliciently toward the left (still referring to Fig. 2) to openthe port or passage E wide the parts or projections B3 of the saidvalve-head will overlap the reduced portion B5 of the bottom of thesteam-chest, and thus allow the steam to pass beneath the saidprojections, rendering them neutral or functionless under the conditionsnamed.

The lower packing-plate part B10 on each side of each valve-head issupported upon a pin B12, made fast in the head. This plate is allowedto move outwardly freely on the pin, whose only function is to hold thelower extremity of the plate Hush with the corresponding extremity ofthe valve-head.

Having thus described my invention, what I claim isM The combination ofa steam-chest whose bottom is curved to conform to the curve of the wallof the cylinder, vertical ports connecting the opposite extremities ofthe cylinder with the opposite extremities of the steamchest, and aslide-valve located in the steamchest and composed of two separatedheads, aV

suitable rigid connection between these heads, andinwardly-projectingparts connected with the heads, the bottom of the steam-chest beingprovided with seats for these projections while the valve-heads arepassing the ports moving inwardly, the bottom of the valvechest beingcut away, to allow the steam to pass underneath the said projections assoon as the heads have opened the steam-ports wide at their inwardtravel.

In testimon y whereof I aflix my signature in presence of two witnesses.

LAFAYETTE M. PETTIT.

Witnesses:

OSCAR L. FAIRLEY, CHAs. D. RAUBER.

